Choose fire blight-resistant varieties and rootstocks, especially in areas outside dry western regions. Most varieties will start to bear significant harvests after 5 to 6 years. Plant at least two different, but compatible, varieties for cross-pollination.
For container-grown trees, remove the plant from its pot and eliminate circling roots by laying the root ball on its side and cutting through the roots with shears. Don't cover the top of the root-ball with backfill because it could prevent water from entering.
Space standard-size trees 20 to 25 feet apart; space dwarf trees 12 to 15 feet apart.
Most of the standard rootstocks are seedlings of the Bartlett variety, producing a tree that can easily grow 25 to 35 feet tall. This rootstock adapts to a wide range of soils, tolerating a certain amount of drought as well as excess soil moisture. It's highly susceptible to fire blight, though, as well as pear root aphids and nematodes. The threat of fire blight may be reduced by choosing a blight-resistant variety grafted onto a Bartlett rootstock.
Bartlett seedlings are winter hardy to zone 5, as are most pear varieties. Seedlings of hardier pear varieties are sometimes used as rootstocks by northern nurseries. Cold-hardy rootstocks of the Siberian pear (Pyrus ussuriensis) and the Snow pear (P. nivalis), are also used, though the Siberian pear rootstock is very susceptible to pear decline, and the Snow pear rootstock is susceptible to fire blight. If you live in zones 2, 3, 4, or the colder sections of zone 5, be sure the pears you order from your nursery are on cold-hardy rootstocks.
In zones 4 and 5 you can try Old Home rootstocks as well. Cuttings of Old Home pear offer a rootstock hardier than Bartlett seedlings. Old Home is resistant to pear decline (a common disease in the West) and moderately resistant to fire blight. However, it is just as susceptible to pear root aphids and nematodes. Old Home rootstock produces a semidwarf tree, 70 percent of standard size.
Cuttings of quince (a different species of fruit) are the most commonly used dwarfing rootstocks for pear, good for zones 5, 6, 7, and 8. It is the rootstock Western commercial growers depend on. Quince rootstock produces a tree about 35 percent of standard size that will bear fruit a year or two sooner.
Quince is not reliably hardy north of the warmer sections of zone 5, and is more sensitive to high soil pH and excess soil moisture than pear. Use it only on sites with excellent air and water drainage and a near-neutral pH. Quince produces a weak root system, and the pear variety tends to overgrow the rootstock, so pears on quince roots should be staked or trellised all their lives. The trees tend to die much sooner than standard pears, sometimes breaking off at the graft union. Quince roots are resistant to pear root aphids and nematodes, and the pear variety on quince resists pear decline. Quince, however, is highly susceptible to fire blight; if it is chosen as a rootstock, choose a blight-resistant variety.
The graft union on a dwarf pear cannot be buried, or the variety roots and overcomes the rootstock's dwarfing effect. However, if Old Home was used as an interstem (you'll see two graft unions), the tree can be planted with the lower union 3 to 4 inches below ground level, and the Old Home interstem will root in 1 to 4 years. The quince root acts as a nurse root for the first few years, inducing earlier fruit production. Old Home becomes the dominant root system, producing a semidwarf tree that's more winter hardy, better anchored, and blight resistant. This is a good choice for zone 5.
For zones 6 and warmer areas, a better fully dwarfing rootstock for pear is OH x F 51. This was the fifty-first seedling of a cross between Old Home and Farmingdale seedlings and is propagated by cuttings. Though not quite as winter hardy as quince and susceptible to nematodes, it's better anchored and resistant to fire blight, pear decline, and pear root aphids. It will produce trees about 50 percent of standard size. Unfortunately, demand for it is great and the supply is low at the present time.
Some West Coast nurseries use the standard-size Oriental pear rootstocks Pyrus betulaefolia and P. calleryana for European pears. Both are highly resistant to fire blight and pear root aphids. However, neither is hardy north of zone 6, and trees on these rootstocks should always be planted with the graft union several inches below ground to protect the rootstock from freezing damage. Betulaefolia roots are highly susceptible to nematodes and induce very vigorous tree growth, so aren't recommended. Calleryana roots are subject to pear psylla and pear decline, but are useful in the Southeast where decline and cold damage aren't problems and fire blight is a severe problem.
